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266 lines
7.9 KiB
XML
266 lines
7.9 KiB
XML
<refentry xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="sec-nix-instantiate">
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<refmeta>
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<refentrytitle>nix-instantiate</refentrytitle>
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<manvolnum>1</manvolnum>
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<refmiscinfo class="source">Nix</refmiscinfo>
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<refmiscinfo class="version"><xi:include href="../version.txt" parse="text"/></refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>nix-instantiate</refname>
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<refpurpose>instantiate store derivations from Nix expressions</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>nix-instantiate</command>
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<group>
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<arg choice='plain'><option>--parse</option></arg>
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<arg choice='plain'>
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<option>--eval</option>
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<arg><option>--strict</option></arg>
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<arg><option>--json</option></arg>
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<arg><option>--xml</option></arg>
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</arg>
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</group>
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<arg><option>--read-write-mode</option></arg>
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<arg><option>--arg</option> <emphasis>name</emphasis> <emphasis>value</emphasis></arg>
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<arg>
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<group choice='req'>
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<arg choice='plain'><option>--attr</option></arg>
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<arg choice='plain'><option>-A</option></arg>
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</group>
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<emphasis>attrPath</emphasis>
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</arg>
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<arg><option>--add-root</option> <emphasis>path</emphasis></arg>
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<arg><option>--indirect</option></arg>
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<group>
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<arg choice='plain'><option>--expr</option></arg>
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<arg choice='plain'><option>-E</option></arg>
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</group>
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<arg choice='plain' rep='repeat'><emphasis>files</emphasis></arg>
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</cmdsynopsis>
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<cmdsynopsis>
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<command>nix-instantiate</command>
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<arg choice='plain'><option>--find-file</option></arg>
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<arg choice='plain' rep='repeat'><emphasis>files</emphasis></arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsection><title>Description</title>
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<para>The command <command>nix-instantiate</command> generates <link
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linkend="gloss-derivation">store derivations</link> from (high-level)
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Nix expressions. It evaluates the Nix expressions in each of
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<emphasis>files</emphasis> (which defaults to
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<emphasis>./default.nix</emphasis>). Each top-level expression
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should evaluate to a derivation, a list of derivations, or a set of
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derivations. The paths of the resulting store derivations are printed
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on standard output.</para>
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<para>If <emphasis>files</emphasis> is the character
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<literal>-</literal>, then a Nix expression will be read from standard
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input.</para>
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<para condition="manual">See also <xref linkend="sec-common-options"
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/> for a list of common options.</para>
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</refsection>
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<refsection><title>Options</title>
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<variablelist>
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<varlistentry>
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<term><option>--add-root</option> <emphasis>path</emphasis></term>
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<term><option>--indirect</option></term>
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<listitem><para>See the <link linkend="opt-add-root">corresponding
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options</link> in <command>nix-store</command>.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--parse</option></term>
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<listitem><para>Just parse the input files, and print their
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abstract syntax trees on standard output in ATerm
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format.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--eval</option></term>
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<listitem><para>Just parse and evaluate the input files, and print
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the resulting values on standard output. No instantiation of
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store derivations takes place.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--find-file</option></term>
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<listitem><para>Look up the given files in Nix’s search path (as
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specified by the <literal linkend="env-NIX_PATH">NIX_PATH</literal>
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environment variable). If found, print the corresponding absolute
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paths on standard output. For instance, if
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<literal>NIX_PATH</literal> is
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<literal>nixpkgs=/home/alice/nixpkgs</literal>, then
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<literal>nix-instantiate --find-file nixpkgs/default.nix</literal>
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will print
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<literal>/home/alice/nixpkgs/default.nix</literal>.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--strict</option></term>
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<listitem><para>When used with <option>--eval</option>,
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recursively evaluate list elements and attributes. Normally, such
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sub-expressions are left unevaluated (since the Nix expression
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language is lazy).</para>
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<warning><para>This option can cause non-termination, because lazy
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data structures can be infinitely large.</para></warning>
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</listitem>
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</varlistentry>
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<varlistentry><term><option>--json</option></term>
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<listitem><para>When used with <option>--eval</option>, print the resulting
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value as an JSON representation of the abstract syntax tree rather
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than as an ATerm.</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--xml</option></term>
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<listitem><para>When used with <option>--eval</option>, print the resulting
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value as an XML representation of the abstract syntax tree rather than as
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an ATerm. The schema is the same as that used by the <link
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linkend="builtin-toXML"><function>toXML</function> built-in</link>.
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</para></listitem>
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</varlistentry>
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<varlistentry><term><option>--read-write-mode</option></term>
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<listitem><para>When used with <option>--eval</option>, perform
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evaluation in read/write mode so nix language features that
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require it will still work (at the cost of needing to do
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instantiation of every evaluated derivation). If this option is
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not enabled, there may be uninstantiated store paths in the final
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output.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<variablelist condition="manpage">
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<xi:include href="opt-common.xml#xmlns(db=http://docbook.org/ns/docbook)xpointer(//db:variablelist[@xml:id='opt-common']/*)" />
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</variablelist>
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</refsection>
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<refsection><title>Examples</title>
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<para>Instantiating store derivations from a Nix expression, and
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building them using <command>nix-store</command>:
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<screen>
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$ nix-instantiate test.nix <lineannotation>(instantiate)</lineannotation>
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/nix/store/cigxbmvy6dzix98dxxh9b6shg7ar5bvs-perl-BerkeleyDB-0.26.drv
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$ nix-store -r $(nix-instantiate test.nix) <lineannotation>(build)</lineannotation>
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<emphasis>...</emphasis>
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/nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26 <lineannotation>(output path)</lineannotation>
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$ ls -l /nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26
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dr-xr-xr-x 2 eelco users 4096 1970-01-01 01:00 lib
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...</screen>
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</para>
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<para>You can also give a Nix expression on the command line:
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<screen>
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$ nix-instantiate -E 'with import <nixpkgs> { }; hello'
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/nix/store/j8s4zyv75a724q38cb0r87rlczaiag4y-hello-2.8.drv
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</screen>
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This is equivalent to:
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<screen>
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$ nix-instantiate '<nixpkgs>' -A hello
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</screen>
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</para>
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<para>Parsing and evaluating Nix expressions:
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<screen>
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$ nix-instantiate --parse -E '1 + 2'
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1 + 2
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$ nix-instantiate --eval -E '1 + 2'
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3
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$ nix-instantiate --eval --xml -E '1 + 2'
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<![CDATA[<?xml version='1.0' encoding='utf-8'?>
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<expr>
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<int value="3" />
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</expr>]]></screen>
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</para>
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<para>The difference between non-strict and strict evaluation:
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<screen>
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$ nix-instantiate --eval --xml -E 'rec { x = "foo"; y = x; }'
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<emphasis>...</emphasis><![CDATA[
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<attr name="x">
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<string value="foo" />
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</attr>
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<attr name="y">
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<unevaluated />
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</attr>]]>
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<emphasis>...</emphasis></screen>
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Note that <varname>y</varname> is left unevaluated (the XML
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representation doesn’t attempt to show non-normal forms).
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<screen>
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$ nix-instantiate --eval --xml --strict -E 'rec { x = "foo"; y = x; }'
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<emphasis>...</emphasis><![CDATA[
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<attr name="x">
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<string value="foo" />
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</attr>
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<attr name="y">
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<string value="foo" />
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</attr>]]>
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<emphasis>...</emphasis></screen>
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</para>
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</refsection>
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<refsection condition="manpage"><title>Environment variables</title>
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<variablelist>
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<xi:include href="env-common.xml#xmlns(db=http://docbook.org/ns/docbook)xpointer(//db:variablelist[@xml:id='env-common']/*)" />
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</variablelist>
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</refsection>
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</refentry>
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